the 3-5% number is just a reference to the total “tax” merchants pay for payment processing as a whole - I get that most of that is the interchange fee that is

the 3-5% number is just a reference to the total “tax” merchants pay for payment processing as a whole - I get that most of that is the interchange fee that is paid out to issuers. but Visa and MC are the ones who dictate the interchange fee rates that issuers receive outside of the Durbin Amendment which capped debit interchange for large banks.